The present invention relates to tires of motor vehicles and more particularly to a pressure indicating device for a tire of a motor vehicle with improved characteristics.
A conventional valve 20 of a tube-less tire is projected from a rim 10 as illustrated in FIGS. 1 and 2. Valve 20 comprises a hollow cylindrical member 30 through rim 10; a tube member 40 having a lower portion secured within a bore of hollow cylindrical member 30 and an upper portion with an outer threaded section 402 and an inner threaded section 401; a channel member 50 having a narrow inner hole; a spring 80; a cap 60 having an outer threaded section 601; and an elongate slender bar 70 having a thin disk 701 on the lower part, with spring 80 anchored between the narrow inner hole of channel member 50 and a top of the elongate slender bar 70. The elongate slender bar 70 is inserted through the channel member 50 and cap 60 until disk 701 is stopped by the bottom end of the channel member 50 which is in turn secured in tube member 40. Also, threaded section 601 of cap 60 is secured to the inner threaded section 401 of tube member 40. In inflating the tire, air is pumped into the tire through bores of cap 60 and channel member 50 by pushing down the elongate slender bar 70 by a needle (not shown) for disengaging disk 701 from the bottom end of the channel member 50. In the mean time, a person can know the fullness of the tire by observing the pivoting of the pointer of a pressure gauge coupled to an air pump. When the tire is in use, the above air passage is dosed. Further, a person can only knock on the tire by hand or foot for generally determining fullness thereof by feeling its hardness or hearing its sound prior to driving. However, such technique is not reliable. Thus, the need for improvement still exists.
It is therefore an object of the present invention to provide an apparatus mounted on a valve of a tire for indicating pressure of the tire. The apparatus comprises a pressure indicator including a downward pipe having an inner thread, a hollow downward cylinder projected into the pipe, the cylinder having a bottom opening, a mainspring having one end coupled to the cylinder, the mainspring being capable of pivoting as air passes through the bottom opening, a pointer coupled to the other end of the mainspring, and a scale. In a mounted state of the pressure indicator and the valve, the inner thread of the downward pipe is secured to the valve, and the cylinder is urged against the valve to form an air path from the tire to the mainspring through the valve and the bottom opening for pivoting the pointer.
It is another object of the present invention to provide an apparatus mounted on a valve of a fire for indicating pressure thereof. The apparatus comprises a pressure indicator including a cap having an inner thread threadably secured to the valve, a hollow downward cylinder projected into the cap and engaged with the elongate slender bar of the valve, the cylinder having a bottom opening, a spring on the cylinder to bias the hollow downward cylinder relative to the cap and away from the elongate slender bar, a mainspring having one end coupled to the cylinder, the mainspring being capable of pivoting as air passes through the bottom opening of the cylinder, a pointer coupled to the other end of the mainspring, and a scale. In a mounted state of the pressure indicator and the valve, the valve is closed when the hollow downward cylinder is not pressed against the bias of the spring. While the spring is compressed, the hollow downward cylinder moves the elongate slender bar to the open position to form an air path from the tire to the mainspring through the valve and the opening for pivoting the pointer.
The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings.